Heat recovery ventilation units are the core components of mechanical supply and exhaust ventilation systems with heat recovery (HRV – Heat Recovery Ventilation). Their purpose is to ensure continuous, controlled air exchange within a building while recovering thermal energy from the air being exhausted outdoors.
Modern solutions, such as the units in our ClimaGold range, combine high energy efficiency with a wide range of applications—from residential construction to public buildings.
How it works
In a heat recovery unit, two independent air streams flow through a heat exchanger but never mix. Warm, stale air from inside the building transfers its energy through the exchanger’s walls to the cold, fresh air coming in from outside. The result is that fresh, filtered air with a temperature similar to that inside the building enters the rooms. Heat recovery efficiency in modern units ranges from 60% to as high as 95%.
Types of Heat Exchangers
The choice of heat exchanger directly affects the efficiency of the entire system. There are three main types:
- Counterflow (cross-counterflow) – air streams flow past each other in opposite directions (efficiency up to 95%). The most popular in modern construction. An example of such a solution is the OPAL COMPACT air handling unit, equipped with a high-efficiency counterflow heat exchanger
- Cross-flow – air streams flow at a 90° angle (efficiency 60–80%). A simpler and cheaper solution to manufacture, but less energy-efficient.
- Rotary (regenerative) – a slow-rotating ceramic or aluminum drum alternately heats up and releases heat. It also enables moisture recovery and is used in commercial installations. The equivalent in the Clima Gold range is the OPAL COMPACT WO air handling unit with a rotary heat exchanger
Construction of a heat recovery unit
A modern ventilation unit with heat recovery is an integrated, multifunctional module consisting of the following components:
- Two EC fans (supply and exhaust) – EC motors allow for precise control of airflow,
- Heat exchanger – the key component responsible for energy recovery
- Air filters – minimum G4 class (traps coarse dust), optionally F7/F9 (pollen, smog, PM2.5, PM10)
- Preheater or bypass system – prevents the heat exchanger from freezing at extreme outdoor temperatures
- Automation and sensors – flow control based on CO₂, humidity, and temperature.
Types of Heat Recovery Units
Modular Heat Recovery Units for Commercial Buildings
For most office, service, and industrial buildings, sectional units that can be configured in a modular fashion are the optimal choice. The OPTIMA STANDARD from our product line is a modern, energy-efficient sectional ventilation and air conditioning unit, designed to serve various types of buildings requiring ventilation and air conditioning. Its wide range of applications and standard technical solutions make it a highly flexible product for implementation.
Rooftop units
For large-volume, open-plan facilities such as production halls, warehouses, or logistics centers, rooftop units are used. A perfect example is the OPTIMA TOP—a ductless rooftop unit mounted directly in a roof opening on a prepared steel base. The unit consists of two functional blocks: an external one located on the roof and an internal one passing through an opening in the ceiling. It handles ventilation, heating, cooling, and heat recovery via a counterflow heat exchanger or a heat pump. A related solution is the OPTIMA ROOFTOP—a dedicated rooftop unit from the Clima Gold range.
Hygienic Air Handling Units
In facilities within the food, pharmaceutical, and medical sectors, strict air purity requirements and easy-to-disinfect equipment are essential. To meet these requirements, we have developed OPTIMA KRYSZTAŁ—a hygienic HVAC unit designed for facilities with heightened sanitary requirements.
Swimming pool and high-humidity zone units
Facilities characterized by high humidity levels, such as swimming pools, spas, water parks, and saunas, require units with a special design resistant to aggressive chemical environments. OPTIMA TURKUS is a swimming pool ventilation and air conditioning unit that ensures thermal and humidity comfort in such spaces. A key feature is the complete separation of both air streams, which 100% prevents contamination of the fresh air. Advanced automation systems precisely control the unit’s operation based on external conditions and usage intensity, minimizing energy consumption.
Air Handling Units for Explosion-Hazardous Areas
In industrial facilities where flammable substances may be present in the air (paint shops, chemical warehouses, refineries), it is necessary to use units that comply with the ATEX directive. OPTIMA EX is a Clima Gold unit manufactured in an explosion-proof version, designed for explosion-hazard zones. Hygienic Air Handling Units
Benefits of heat recovery in ventilation units
- Energy savings – reduction in heating and cooling costs by up to 30–50% annually
- Consistent air quality – continuous filtration removes pollen, smog, allergens, and excess CO₂ without opening windows
- Protection against moisture and mold – controlled ventilation prevents water vapor condensation on building partitions
- Acoustic comfort – modern units operate quietly, especially in night mode
- Compliance with building codes – in new energy-efficient buildings (WT 2021 and higher standards), mechanical ventilation with heat recovery is virtually indispensable.
Selection and Installation
Proper selection of a ventilation unit with heat recovery requires prior calculation of the ventilation air demand, which depends on the building’s volume, the number of occupants, the type of rooms, and technological requirements.
